In engines having a supercharger, there have been various proposals to date for providing a turbo sensor that detects the rotational speed of the supercharger and controlling, based on a detection signal from the turbo sensor, an operating state of an engine main unit that has a correlation with the rotational speed of the supercharger (see, for example, Patent Documents 1 to 3).
However, those proposed so far are premised on that the turbo sensor properly operates, and a means that takes a malfunction of the turbo sensor into consideration does not exist.